Schizophrenic patients show extensive attentional and cognitive deficits. Event-related potentials (ERP) provide a "window" into brain information processing mechanisms and an objective measure of cognitive deficits associated with schizophrenia. This project will utilize auditory and visual ERPs to investigate attention and memory in first-episode and chronic schizophrenics. Deficits in the generation of auditory P3, a long latency cognitive ERP component, that depends upon active concentration or 'paying attention', has been one of the most consistently observed neurophysiological abnormalities associated with schizophrenia. Recent studies have demonstrated that schizophrenia is associated with abnormalities in the generation of other cognitive components as well. MMN is a component that occurs when the brain automatically detects changes in the environment even when subjects are not paying attention. Recently it has been shown that MMN is abnormal in chronic schizophrenics. MMN has not yet been investigated in first-episode patients, so we do not know when during the course of the illness MMN becomes abnormal and whether the abnormality occurs in all subjects or only in those with persistent symptoms. Because MMN is an index of a very simple automatic brain process, deficits in MMN generation would suggest more pervasive brain dysfunction than would deficits in P3 alone. As opposed to P3 which is a trait marker for schizophrenia irrespective of clinical outcome, MMN may be abnormal in chronic, but not remitted schizophrenics, and may serve as a predictor of good vs poor outcome in first-episode patients. The visual P3 provides a parallel index of visual working memory. Our recent preliminary study showed that a heterogeneous group of schizophrenics showed a disinhibition of the visual P3, suggesting visual working memory impairments. Whereas auditory P3 is uncorrelated with clinical state and is thought to be a vulnerability trait marker, visual P3 is correlated with clinical improvement and has the characteristics of a state marker in schizophrenia. Therefore visual P3 may be abnormal in symptom-rich first-episode patients but may normalize with clinical improvement in stable chronic patients. One of the greatest challenges in schizophrenia research is to develop markers that can differentiate between good and poor prognosis schizophrenics. We will utilize a task in which we can simultaneously investigate MMN, auditory P3 and visual P3. We will compare first-episode schizophrenics, chronic schizophrenics and normal controls on these ERP measures and relate ERP measures to clinical ratings and psychological tests.